A model for assessment of potential geographical
accessibility: a case for GIS.

Abstract:

Health is geographically differentiated thereby creating an
inextricable link between "place" and "health".
Differences in access to healthcare services and resulting adverse
health outcomes when there is inadequate healthcare are major public
health priorities. While the literature is replete with research about
disparities in healthcare access and health outcomes, a greater
understanding of geographical enabling factors and predisposing
characteristics is needed. The purpose of this concept article is to
present a discussion of development of a theoretical framework for study
of potential geographical access to healthcare from a perspective of
Andersen's Behavioral Model of Health Services Use (Andersen,
1995). An adaptation of Andersen's model, The Model for Ne
Assessment of Potential Geographical Accessibility, is presented as a
conceptual framework to aide in future studies of potential geographical
accessibility. The application of geographical information systems (GIS)
technology and methodology as an analytical tool will also be presented.

Differences in access to healthcare services and the resulting
adverse health outcomes are major public health priorities. The
Institute of Medicine (IOM, 2002) and the Department of Health and Human
Services (USDHHS, 2000), identified the need for strategies to improve
access to healthcare services and to support improvement of health
outcomes (AHRQ, 2002; IOM, 2002). Furthermore, Healthy People 2010
designates two central goals for the nation's health: (a) to
increase quality and years of healthy life, and (b) to eliminate health
disparities (USDHHS, 2000). Many studies have been conducted to identify
the characteristics of disparities in healthcare access and health
outcomes. Findings of these studies indicate that while most Americans
have high quality healthcare available, gaps or disparities in
healthcare access and health outcomes continue to exist. These
disparities are associated with age, education, race and ethnicity,
gender, income and socioeconomic status (SES), and place of residence
and location of healthcare services.

Healthcare policy changes over the past decade have drastically
decreased access to healthcare services. The rural health environment
has been impacted by these changes in many ways (Bushy, 2000; Folland,
et al., 2001). Significant decreases in healthcare services to an
already vulnerable, at-risk rural population have compounded existing
problems of resource disparities. Loss of community health services,
healthcare professional shortages, rapidly rising cost, hospital
closures, homecare cut backs, and tighter government payment schedules
are just a few of the changes that have led to greater resource
disparities for rural populations (USDHHS, 2000; Eberhardt, et al.,
2001). Because of structural, financial and sociocultural barriers in
rural populations, they have fewer healthcare resources than urban
populations. These rural resource disparities often lead to comlex
adverse health outcomes and rural health status disparities (Fryer, et
al., 1999; Lovett, Haynes, Sunnenberg, & Gale, 2002; Lin, Allen,
& Penning, 2002).

While the amount of research about disparities in healthcare access
and health outcomes is overwhelming, there is a paucity of literature
that provides a greater understanding of geographical enabling factors
and predisposing characteristics. More information about the
relationship between and the effect of social and geographical factors
that enable people to obtain healthcare is needed. Specifically, are
healthcare services located in a manner that allows equal access?
Research linking specific types of mortality of specific regions of the
country to access to specific types of healthcare services could provide
information to assist in the reduction of the excess mortality found in
at-risk populations.

Andersen's Behavioral Model of Health Services Use has often
been used as a framework for the assessment of healthcare access,
outcomes, and quality. Within this framework is embedded the premise
that the lack of timely access to healthcare services may potentially
cause adverse health outcome as evidence by higher mortality rates.

FRAMEWORK FOR THE STUDY OF ACCESS

R.M. Andersen began to examine the concepts of "access"
in 1968. His seminal work explored "systems" and
"behavior" of medical care and identified and defined concepts
of "access" (Andersen, 1970). Andersen, along with L. A. Aday,
further examined concepts of access in a comprehensive literature review
(Aday & Andersen, 1974). This work both conceptualized and
operationalized "access" to medical care and provided an
integrated theoretical framework for use in the study of access to
medical care. In these works, the authors showed how empirical
indicators could be derived from the concepts of access. Later Andersen
updated this framework of access to a behavioral model of health
services use (Figure 1) (Andersen, 1995). Today, concepts of
Andersen's model remain relevant and are used as a framework for
assessment of healthcare access, outcomes, and quality (Love, et al.,
1995; Fryer, et al., 1999; Phillips, et al., 2000; Henton, et al., 2002;
Leong-Wu & Fernandez, 2006; Lo & Fulda, 2008.

[FIGURE 1 OMITTED]

Note. From Revisiting the behavioral model and access to medical
care: Does it matter? By R. M. Andersen, 1995, Journal of Health and
Social Behavior, 36, (March) 1-10. Reprinted with permission.

The concepts identified by Andersen within a framework for study of
access are defined (Andersen, 1995). In Table 1 these concept
definitions provide a clear basis for understanding the application of
the model.

Andersen's original Behavioral Model of Health Services Use
was initially developed in the late 1960's to help understand the
use of health services; to define and measure equitable access to
healthcare; and to assist in health policy development to promote equal
access to healthcare (Andersen, 1995). In the revised "Behavioral
Model of Health Services Use" Andersen posits that health service
use is a function of people's predisposition to use services,
factors that enable or impede use, and their need for care (Andersen,
1995). These factors make individual contributions in prediction of
healthcare use.

Predisposing characteristics include demographic factors, social
structure factors, and health beliefs. Biological imperatives such as
age and sex would be included in demographic factors that might explain
the need for healthcare. Measures of social structure are education,
occupation, ethnicity, as well as social networks, social interactions,
and culture. It is Andersen's position that while health beliefs
add to the model's ability to explain health services use in
general, measures of enabling resources and need explain more of the
variation. In assessment and measurement of "enabling
resources" Andersen further challenges researchers to go beyond
obvious measures of "regular source of care", "physician
populations" and "hospital bed counts". Andersen believes
that for healthcare service utilization to happen, it is imperative that
both "personal enabling resources" and "community
resources" be socially and geographically available. The kinds and
types of health services available where people live as well as their
organizational structure and process are important factors.

Both community and personal enabling resources must be present for
use to take place. First, health personnel and facilities must be
available where people live and work. Then, people must have the means
and know-how to get to those services and make use of them. Income,
health insurance, a regular source of care, and travel and waiting times
are some measures that can be important here (Andersen, 1995).

One of the strongest determinants of this model of health service
use is the "need" factor. Andersen presents "need"
as perceived health status, evaluated health status, or consumer
satisfaction. He sees perceived health status as a social phenomenon
that is explained by social structure and health beliefs. Evaluated
health status is a biological imperative represented by
"professional judgment" about health status (i.e. functional
status, mortality, and morbidity, etc.). These biological and social
components are dynamic and interrelated and vary with changes in
medicine and medical care that is driven by technology, policy, and
geography. Evaluated need (such as mortality) is most related to
"kind and amount of medical care provided" (Andersen, 1995).

A more specific model for assessment of access can help with
understanding the health status of specific populations in relationship
to the provision of specific health services. Evaluation of specific
small-area "need" and the relationship to that area's
predisposing factors and enabling resources can change health outcomes.
Assessment of mortality rates and the relationship to location or
distance to health services can improve mortality rates. A Model for
Assessment of Potential Geographical Accessibility (See Figure 2) is
presented for the study of diseases by specific geographical areas. This
model was originally adapted from Andersen's "Behavioral Model
of Health Services Use" to guide a study of access to cardiac
intervention services in Alabama and Mississippi (Author, 2007). The
model provides a framework that can be replicated or modified based on
specific healthcare systems, predisposing characteristics, enabling
resources, need, or health status variables to guide studies of access
and health outcomes.

[FIGURE 2 OMITTED]

HEALTHCARE ACCESS

Access as defined by Andersen is the "ability to use health
services when and where they are needed" (Andersen, 1995). Cromely
& McLafferty further describe access as the "power to command
health service resources" (2002). Potential access or the
population's potential for access is more simply defined as the
"presence of enabling resources" (Andersen, 1995). The lack of
enabling resources can lead to decreased access to healthcare services.
Barriers of access such as race, age, education, income, sex, culture,
ethnicity, sexual orientation, lack of insurance, and geographical
location can affect the use of healthcare services (Cromley &
McLafferty, 2002; AHRQ, 2002).

The concept of access is multidimensional. Dimensions of access
include availability, accessibility, accommodation, affordability, and
acceptability. Aday and Andersen further divide accessibility into
socio-organizational and geographical aspects (1974). The geographical
dimension of access includes empirical measures such as distance, travel
time, transportation, and the associated cost. Measures of access often
focus on geographical location of service "provision" and the
relationship to the population in "need". Both
"time" and "space" create constraints to access
(Cromley & McLafferty, 2002). Therefore, the location of healthcare
services and the associated distance and travel time are important
health policy issues.

Over thirty years ago Julian Tudor Hart described the imbalance
between "need" and "provision" of healthcare
services in Great Britain (Hart, 1971). Hart's seminal research
described class gradients in mortality and morbidity in Britain and
proposed that a more "just" distribution of healthcare
resources would subsequently equalize the social and geographical
differences in health outcomes such as mortality. The "inverse care
law" proposed by Hart stated that "the availability of good
medical care tends to vary inversely with the need for it in the
population served" and that this law "operates more completely
where medical care is exposed to market forces, and less so where such
exposure is reduced" (USDHHS, 2000). The inverse relationship
between "need" for healthcare and "provision" of
healthcare continues to exist despite advances in healthcare. Current
literatures suggest that this phenomenon is evident in healthcare in
both developed and undeveloped countries.

Need is most often assessed using population characteristics and
risk factors such as population distribution, age, sex, income, etc. But
need is more than a function of population distribution and other
population characteristics. Need is better defined by burden of disease
indicators such as morbidity and mortality data. Mortality data have
been widely used as an indicator or surrogate for health status or
healthcare needs evaluation (Gatrell, 2002). Where high rates of
mortality exist, there is a high burden of disease. Mortality data can
indicate the geographical areas where resources are most needed.
Research relating mortality data to the geographical location of
healthcare services by specific diseases and procedures can help
healthcare planners and policy makers achieve equitable distribution of
resources. Geographical resource distribution studies are needed to
describe and analyze inequity in the spatial distribution of healthcare
resources and the relationship to burden of disease.

ACCESS AND HEALTH OUTCOMES

Health status is an outcome of multiple determinants. Individual
biology and behaviors, physical and social environments, policies and
interventions, and access to quality healthcare are predisposing factors
that can contribute to the health of people and communities (USDHHS,
2000; Eberhardt, et al., 2001; Ricketts, 1999). These predisposing
factors for health status are often interdependent and interrelated
creating a complex web of causation for health outcomes (Bushy, 2000;
Friedman, 1994).

There are many structural, financial, and socio-cultural barriers
to access to quality healthcare. These barriers are an integral part of
the complex web of causation of many disease processes because they
affect health-seeking behaviors, health service utilization, and
ultimately may lead to adverse health outcomes (Bushy, 2000; Friedman,
1994).

According to Andersen (1995), health outcomes are measured and
defined by health status, satisfaction, and quality of life. Dunkin
states that outcomes are "complementary in measuring access,
especially for complex chronic health problems" and "can
provide insight about barriers that may impede access to services"
(Dunkin, 2000).

Over the years many studies have documented differences in health
outcomes as well as challenges that groups experience in accessing
quality healthcare (Blustein & Weitzman, 1995; Black, et al., 1995;
Weitzman, et al., 1997; Bullen, et al., 1996; Goodman, et al., 1997).
Differences in health outcomes and health status are referred to as
"healthcare disparities". When there are differences or
variations in health outcomes among populations, inequality in
healthcare access is a valid assumption (AHRQ, 2002). Inequalities also
exist when all patients do not have access to care that meets the
standards for "best practice". These inequalities create
underserved, at-risk populations and have been identified by Congress as
priority populations. These groups include women, children, the elderly,
minority groups, low-income groups, residents of rural areas, and
individuals with special healthcare needs varying across regional and
geographical areas of the country. Priority populations are the targets
of many health initiatives directed toward identifying strategies to
improve access and health outcomes (AHRQ, 2002; USDHHS, 2000). One such
strategy could be the use of GIS for assessment of healthcare access and
health outcomes.

A CASE FOR GIS

Geographic Information Systems (GIS) are a growing technology and
methodology. GIS are computer-based information systems that combine
mapping capabilities with data referenced by spatial or geographic
coordinates. They can capture, organize, store, manipulate and analyze
spatial data. GIS can link and join geographical features on a map with
attribute data as well as query databases to produce patterns of health
outcomes (Gatrell, 2002). They can produce maps beneficial for medical
geography.

GIS are important tools for showing inequalities in health between
regions. Because where healthcare is located matters, GIS analysis of
health data and healthcare service locations is valuable for describing
and understanding relationships between healthcare access and health
outcomes. Mapping of health data can establish patterns of health
disparities.

The World Health Organization (WHO, 2003) identifies the value of
public health mapping and GIS. According to the WHO

The literature is replete with reports of regional, locational, and
small-area analysis of health disparities (Bullen, et al., 1996; Andrews
& Phillips, 2002; Bamford, et al., 1999; Haynes, et al., 1999). GIS
is effective in the management and analysis of health data at these
levels. Analysis at the census tract or county level is important in the
identification of patterns of healthcare outcomes and the association or
linkage to political processes and policy makers (Cromley &
McLafferty, 2002; Gatrell, 2002; Elliot, et al., 2000; Meade &
Earickson, 2000).

SUMMARY

The United States Department of Health and Human Services
identifies in its national health initiative the priority that all
people, including the most vulnerable, should have health that allows
them to have a productive life by the year 2010 (USDHHS, 2000).
Healthcare access is becoming increasingly complex as a growing and
diverse population and rapid healthcare reform continue to modify the
provision of healthcare services. Improving healthcare access, reducing
geographical variability in health outcomes, and eliminating disparities
are major social and political issues.

Many disparities exist within the current United States healthcare
system. These inequalities have been shown to restrict healthcare access
and lead in regional health outcome disparities. Decreasing access
contributes to patterns of excessively high disease incidences,
morbidity, and mortality.

Because the match between "need" and
"provision" is an important determinant of equitable access
more studies are needed in describe specific geographical patterns of
health. The literature supports the use of small-area analysis for the
study of access. Andersen's Behavioral Model of Health Service Use
provides one approach to the assessment of access to healthcare
services. Application of the adapted Model for the Assessment of
Potential Geographical Accessibility (See Figure 2) provides an
opportunity to evaluate the specific relationship between location and
"provision" of healthcare and mortality rates or
"raced". It can provide a guide for future studies of
healthcare access. The model can be modified by using other healthcare
services, predisposing characteristics, enabling resources, healthcare
need, or by other health outcomes or health status variables.

Further research is also needed in the use of GIS to both visually
identify and empirically measure spatial relationships of geographical,
environmental, and social influences of disease. More research of
predisposing characteristics and enabling factors for other specific
populations is needed.

GIS is becoming instrumental in the synthesis of information to
foster awareness of specific health concerns, facilitate development of
intervention strategies, and enhance utilization of resources. GIS
technology can be of great value in health planning, the development of
health policies and the allocation of healthcare resources.

Regional disparities in mortality rates observed can provide
valuable starting points for the analysis of healthcare service
accessibility. With further analysis, those responsible for the
development of healthcare policy can modify healthcare services and
define quality healthcare sensitivity and responses to these issues of
decreased access and excess mortality. Social justice requires the
reversal of healthcare inequalities by better distribution of resources.
Healthcare policy must not neglect the vulnerable populations created by
geographical inequality.

U.S. Department of Health and Human Services (USDHHS) (2000).
Healthy people 2010: National health promotion and disease prevention
objectives. Washington, DC: U.S. Department of Health and Human
Services.

Geographical information systems (GIS) provide ideal platforms for
the convergence of disease-specific information and their analyses
in relation to population settlements, surrounding social and
health services and the natural environment. They are highly
suitable for analyzing epidemiological data, revealing trends and
interrelationships that would be difficult to discover in tabular
format. Moreover GIS allows policy makers to easily visualize
problems in relation to existing health and social services and the
natural environment and so more effectively target resources.

Table 1
Concepts within a framework for the study of access
Concept Definition
Health Policy Andersen (1995) suggests that it is the
evaluation of the effect of health policy
that health planners and policy makers
are most concerned about.
Characteristics of the Specifically, "delivery system"--"those
Healthcare Delivery System arrangements for the potential rendering
a. Resources of care to consumers" (Andersen, 1995).
i. Organization a. Resources--the labor and capital
ii. Entry devoted to healthcare. These
iii. structure resources include health personnel,
physical structures, equipment, and
materials for the provision of
healthcare and are assessed by both
volume and distribution of services.
i. Organization--"what the
system does with its
resources. It refers to the
manner in which medical
personnel and facilities are
coordinated and controlled in
the process of providing
medical services" (Andersen,
1995)
ii. Entry--process of gaining
entrance into the healthcare
system and can be measured in
terms of travel time, waiting
time, etc. Another term for
entry is "access".
iii. Structure--includes whom the
patient sees and how he is
treated as measures of what
happen to the patient after
entering the system.
Characteristics of the Individual's determinants of health
Population at Risk service use.
a. Predisposing a. Predisposing component--variables
component that exist before the onset of the
b. Enabling component illness that describe the individual
c. Need component propensity to use services. Measures
of this component include age, sex,
race, religion, and values about
health and illness.
b. Enabling component--means or
resources individual have available
for the use of services. Individual
or family resources include income
and insurance coverage, while
attributes of the community of
residence include rural-urban
character and region.
c. Need component--level of illness
that brings about health service
use. May be perceived by the
individual or evaluated by delivery
system.
Utilization of healthcare External validation of the effect of the
services characteristics of the population at risk
a. Type and of the delivery system on entry (or
b. Site non-entry) into the system. Andersen
c. Purpose (1995) state that health policy makers
d. Time interval are concerned with both those who do and
do not get into the healthcare system.
a. Type--kind of services received
(hospital, physician, pharmacy,
etc.)
b. Site--place where the service is
received.
c. Purpose--whether care is preventive
in nature, illness-related, or
custodial. These reason or purposes
for care have different patterns
of care seeking in the concept of
access. The purpose of health
services is important to the
understanding of the specific
healthcare demands of those who
seek healthcare services.
d. Time interval--is measured in terms
of contacts, volume, or continuity
measures.